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Re: const or constant?

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Stefan Ram wrote:
> Ian Collins <ian-news@hotmail.com> writes:
>> Stefan Ram wrote:
>>> Ian Collins <ian-news@hotmail.com> writes:
>>>>> 1) Declaring that a function will not modify its arguments
>>>>> 2) Declaring that an object resides in ROM (read only memory)
>>>> That's what C++ constexpr supports.
>>> »constexpr« in C++ marks entities whose value is known or
>>> can be calculated at compile time.
>> Correct.  It goes further in guaranteeing the value is generated at
>> compile time.  It is this guarantee that enables constexpr values to be
>> stored in read only memory.
>
>    [OT: this is about "constexpr" in C++]
>
>    Some constexpr values are not stored at runtime at all.
>
>    For example:
>
> #include <iostream>
> #include <ostream>
>
> constexpr int factorial( int const i )
> { return i > 0 ? i * factorial( i - 1 ): 1; }
>
> int main(){ constexpr int i = factorial( 5 );
>    if( i < 5 )::std::cout<< "alpha\n"; }
>
>    A C++ compiler with some optimizations enabled
>    should compile the above program to the same as:
>
> int main() {}
>
>    . There are variables and values in the source code,
>    but nothing is stored at runtime.

Well what else would you expect in that example?  All you have done with 
constexpr is helped the compiler with its optimisation.

If i were required to be visible outside of main, it would have to exist 
and would be in read only memory (which might be as a literal constant 
the in the executable code).

-- 
Ian Collins

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const or constant? jacob navia <jacob@spamsink.net> - 2014-04-22 18:58 +0200
  Re: const or constant? "Bill Cunningham" <nospam@nspam.invalid> - 2014-04-22 14:13 -0400
    Re: const or constant? Barry Schwarz <schwarzb@dqel.com> - 2014-04-22 15:59 -0700
  Re: const or constant? jt@toerring.de (Jens Thoms Toerring) - 2014-04-22 21:26 +0000
    Re: const or constant? James Kuyper <jameskuyper@verizon.net> - 2014-04-22 17:56 -0400
      Re: const or constant? Keith Thompson <kst-u@mib.org> - 2014-04-22 15:32 -0700
        Re: const or constant? James Kuyper <jameskuyper@verizon.net> - 2014-04-23 08:57 -0400
          Re: const or constant? David Brown <david.brown@hesbynett.no> - 2014-04-23 15:27 +0200
            Re: const or constant? Keith Thompson <kst-u@mib.org> - 2014-04-23 08:34 -0700
              Re: const or constant? David Brown <david.brown@hesbynett.no> - 2014-04-24 08:50 +0200
                Re: const or constant? James Kuyper <jameskuyper@verizon.net> - 2014-04-24 07:58 -0400
                Re: const or constant? David Brown <david.brown@hesbynett.no> - 2014-04-24 14:19 +0200
                Re: const or constant? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-04-24 21:40 +0000
                Re: const or constant? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-04-25 01:05 -0700
          Re: const or constant? "BartC" <bc@freeuk.com> - 2014-04-23 21:38 +0100
      Re: const or constant? jacob navia <jacob@spamsink.net> - 2014-04-23 00:51 +0200
    Re: const or constant? jacob navia <jacob@spamsink.net> - 2014-04-23 00:47 +0200
  Re: const or constant? Walter Banks <walter@bytecraft.com> - 2014-04-22 18:00 -0400
  Re: const or constant? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-04-22 23:12 +0100
    Re: const or constant? jacob navia <jacob@spamsink.net> - 2014-04-23 01:00 +0200
      Re: const or constant? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-04-23 14:48 +0100
        Re: const or constant? Keith Thompson <kst-u@mib.org> - 2014-04-23 08:40 -0700
          Re: const or constant? jacob navia <jacob@spamsink.net> - 2014-04-23 21:49 +0200
            Re: const or constant? Kaz Kylheku <kaz@kylheku.com> - 2014-04-23 20:11 +0000
            [OT] Killfiles (was Re: const or constant?) Keith Thompson <kst-u@mib.org> - 2014-04-23 14:49 -0700
              Re: [OT] Killfiles (was Re: const or constant?) Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-04-23 22:22 -0700
    Re: const or constant? James Kuyper <jameskuyper@verizon.net> - 2014-04-23 09:09 -0400
  Re: const or constant? Ian Collins <ian-news@hotmail.com> - 2014-04-24 09:35 +1200
    Re: const or constant? Ian Collins <ian-news@hotmail.com> - 2014-04-24 10:06 +1200
      Re: const or constant? Ian Collins <ian-news@hotmail.com> - 2014-04-24 10:52 +1200

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